MSET: DeleteRef Exception

apple.awt.EventQueueExceptionHandler Caught Throwable :
java.lang.NullPointerException
java.lang.NullPointerException
at
document.mset.SubNodeView.getDeleteRefUpdate(SubNodeView.java:450)
at
document.mset.MSET$DeleteRef.getUpdate(MSET.java:714)
at document.mset.MSET.delete(MSET.java:214)
at
document.mset.MSETDocClient$InboundEdit.run(MSETDocClient.java:338)
at
java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:189)
at
java.awt.EventQueue.dispatchEvent(EventQueue.java:478)
at
java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:234)
at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:184)
at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:178)
at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:170)
at
java.awt.EventDispatchThread.run(EventDispatchThread.java:100)